Fair Value Measurement - Transfers (Details) (USD $) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	$ 2.3
Recurring | Derivative liability | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, level 3 to level 2 transfers	4.4		1.2
Recurring | Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, level 3 to level 2 transfers	1.3	1.3	1.8
Liabilities, level 2 to level 3 transfers	1.0
Recurring | Other borrowed funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, level 2 to level 3 transfers	1.1
Recurring | Derivative asset | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	4.3
Recurring | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	2.3
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	2.0
Recurring | Margin loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	2.6
Recurring | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	2.7
Assets, level 2 to level 3 transfers	1.1
Recurring | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers		27.4
Recurring | Trading assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers		1.4
Assets, level 2 to level 3 transfers		1.4
Recurring | Mortgage-backed securities, U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 1 to level 2 transfers		$ 113.9